Fighting in the war-torn Nuba mountains in Sudan has led to an increase in the number of Sudanese refugees fleeing to South Sudan in the last month. In addition to an estimated 1.4 million internally displaced people, South Sudan is also now home to around 250,000 Sudanese.

Yida camp in South Sudan's Unity State, one of the country's biggest refugee settlements, now shelters more than 80,000 refugees.

Everyone in Yida fled from a single conflict across the border in Sudan's South Kordofan state. U.N. officials say there has been a rapid rise in the numbers arriving because of recent heavy clashes.

“We have seen an almost 100 percent increase in the last month when compared to the same period in 2013 and 2014, meaning nearly 700-900 people every week coming to South Sudan,” said Rocco Nuri form the U.N. High Commission for Refugees.

A bloody civil war has raged for more than three years in Sudan's Nuba mountains -- with yearly fighting between Sudan Government forces (SAF) and Sudan's Peoples Liberation Army, North rebels (SPLA-N).

The spreading ground fighting, intensified bombing by the government's planes and poor food security force thousands of families to flee.

"Whether you run or not, they bombard and kill you either way, Ismail added. "We had neighbors who were hiding indoors one time when an Antonov came, but their house was bombed and they were killed.”

People arrive with what they could carry. Gelila Abreham, who arrived only a few days ago, said it took her one week to walk here from her village with her three children.

"We came here because they continue to bombard us day and night," she said. "That is why we ran away. We move from one place to another because they follow us to wherever we go and bomb us."

Many new arrivals will travel to Ajoung Thok, a U.N. camp to the east. But with a capacity for only 25,000, it is almost full.

While Sudan's government denies it, Yida camp director Yacoub Osman Kaluka said the bombing is intentionally driving civilians out of South Kordofan.

“Their objective is to scare people and to make them run away from the SPLA-N-controlled area," he said. "They do that by burning all the crops in the fields, burning the houses and giving them no rest, so they will evacuate ... to empty the Nuba mountains of human beings so it will just remain a no-mans land.”

Life in Yida camp is basic, but safe. People have access to fresh water and health care with help from humanitarian groups. It is unkown how long the refugees will stay, but after peace talks failed last year, many think they may never return home.

A recent arrival, Gisma Musa Farjala, said her family used to farm before the war.

“But after the bombardment started we could not continue with that," Farjala added. "We lost our parents, and our children lost their fathers, and life has become so difficult for us. Before the war we used to live well, but now we don’t.”

Meanwhile, UNHCR said another new camp will soon be established to prepare for a surge of refugees expected from across the border in the coming months.